Method and apparatus for powering an electric hand-held power tool device

1. An apparatus for powering an electric hand-held power tool device with an output voltage comprising at least two connectors for connecting said apparatus to at least two batteries at least two switches a command circuit of said switches, said command circuit being arranged for commanding said switches so as to power said electric hand-held power tool device by using the battery which presents the highest open circuit voltage if said output voltage is higher than the open circuit voltage of each of the other battery (ies); the battery which presents the highest open circuit voltage and at least one other battery if said output voltage is lower than the open circuit voltage of said other battery, said battery which presents the highest open circuit voltage and said at least one other battery being connected in parallel.

2. The apparatus of claim 1 , further comprising at least two connecting switches arranged for allowing a unidirectional and/or bidirectional flow of current between said at least two switches and said at least two batteries.

3. The apparatus of claim 1 , further comprising a main switch for activating/deactivating said apparatus.

4. The apparatus of claim 1 , further comprising a passive hot plug circuit for pre-charging said device.

5. The apparatus of claim 1 , said command circuit further comprising a DSP circuit.

6. The apparatus of claim 1 , further comprising at least one power bridge capacitor.

7. The apparatus of claim 6 , further comprising at least two measurement points for measuring the voltage of each of said at least two batteries a measurement point for measuring the voltage of said main switch a measurement point for measuring the voltage across said power bridge capacitor.

8. A method for powering an electric hand-held power tool device by an output voltage of an apparatus, comprising connecting said apparatus to at least two batteries by using at least two connectors commanding at least two switches so as to power said electric hand-held power tool device by using the battery which presents the highest open circuit voltage if said output voltage is higher than the open circuit voltage of each of the other battery (ies); the battery which presents the highest open circuit voltage and at least one other battery if said output voltage is lower than the open circuit voltage of said other battery, said battery which presents the highest open circuit voltage and said at least one other battery being connected in parallel.

9. The method of claim 8 , further comprising allowing a unidirectional and/or bidirectional flow of current between said at least two switches and said at least two batteries by using at least two connecting switches.

10. The method of claim 8 , further comprising activating/deactivating said apparatus by using a main switch.

11. The method of claim 8 , further comprising a passive hot plug procedure for pre-charging said device.

12. The method of claim 10 , further comprising checking at least two measurement points for measuring the voltage of each of said at least two batteries a measurement point for measuring the voltage of said main switch a measurement point for measuring the voltage of a power bridge capacitor.

13. A computer-program product for causing an apparatus to power an electric hand-held power tool device by an output voltage comprising instructions executable to command at least two switches for powering said electric hand-held power tool device by using a battery which presents the highest open circuit voltage if said output voltage is higher than the open circuit voltage of each of the other batteries the battery which presents the highest open circuit voltage and at least one other battery if the said output voltage is lower than the open circuit voltage of said other battery, said battery which presents the highest open circuit voltage and said at least one other battery being connected in parallel.